The present invention relates to a polyester-based photographic support and a production process thereof. More particularly, the present invention relates to a photographic support comprising a polyester film and an undercoat having high adhesion to the photosensitive layer provided on the support, and a production process thereof.
Polyester films represented by polyethylene terephthalate film and polyethylene-2,6-naphthalate film, are suitable for use as a photographic support because of their excellent chemical and physical properties such as mechanical strength, dimensional stability, transparency and flatness, and have practically been used popularly for this purpose. Polyester films, however, also have a disadvantage of poor surface activity, especially low adhesion to the photosensitive layer formed on the support by topcoating it with a photographic emulsion using a gelatin-based binder.
Secure adhesion of the photosensitive layer to the support is essential not only when the finished photographic material is dry but also when it is still in a wet state during photographic treatments such as development.
Therefore, in case where a polyester film is used as a photographic support, there is usually formed on the film a layer of a certain type of polymer, which can serve as an easily adhesive layer, before providing the photosensitive layer.
Specifically, it is known to provide a layer of a polyester copolymer, a vinylidene chloride copolymer, a mixture of gelatin and a hydrophilic vinyl or acrylic copolymer, a carboxy-modified polyethylene or the like as the above-mentioned easily adhesive layer. Also, in some cases, the polyester film is subjected to a pretreatment such as corona discharge treatment before providing the polymer layer.
However, the above-mentioned methods have the following problems. (A) A thicker easily adhesive layer is required so as to achieve adhesive properties for practical use. Namely, an improvement of adhesive properties is insufficient. (B) When cut scrap polyester film having easily adhesive layer is recycled, the obtained film is undesirably colored. For example, when cut scrap polyester film having polyvinylidene chloride coat is recycled, melted and processed to form a film, there are problems that chlorine gas is generated, the apparatus for film production is corroded by chlorine and the produced film is undesirably colored. These problems become serious when the thicker easily adhesive layer is used so as to overcome the above problem (A). (C) The improvement of adhesive properties by conducting corona discharge-treatment is more insufficient than that by providing easily adhesive layer.
Therefore, there is a strong demand to provide a polyester film having an easily adhesive layer which causes no problems descried in the above.
As a result of the present inventor's earnest studies to solve the above problems, it has been found that a polyester film obtained by applying a coating solution containing an aqueous polyester and an aqueous epoxy group-containing compound in a specific ratio on at least one side of the polyester film and drying the coat, shows high adhesiveness to the photosensitive layer and is suited for use as a polyester-based photographic support.
The present invention has been attained on the basis of the above finding.